Enhancing imaging by multicore fiber endoscopes

ABSTRACT

Multicore fibers and endoscope configurations are provided, along with corresponding production and usage methods. Various configurations include an adiabatically tapered proximal fiber tip and/or proximal optical elements for improving the interface between the multicore fiber and the sensor, photonic crystal fiber configurations which reduce the attenuation along the fiber, image processing methods and jointed rigid links configurations for the endoscope which reduce attenuation while maintaining required flexibility and optical fidelity. Various configurations include spectral multiplexing approaches, which increase the information content of the radiation delivered through the fibers and endoscope, and configurations which improve image quality, enhance the field of view, provide longitudinal information. Various configurations include fiber-based wave-front sensors. Many of the disclosed configurations increase the imaging resolution and enable integration of additional modes of operation while maintain the endoscope very thin, such as spectral imaging and three dimensional imaging.

BACKGROUND OF THE INVENTION 1. Technical Field

The present invention relates to the field of endoscopy, and moreparticularly, to multicore fiber endoscopes.

2. Discussion of Related Art

Endoscopes in various configurations allow efficient treatment of arange of medical problems, as well as means for manipulating differentsituations with limited access. Endoscope operations are challenging inthat illumination, detection and treatment are confined to long andnarrow operations modes. Fiber optics technology is a central enablerfor such techniques, and fiber-based endoscope experience continuousimprovements.

SUMMARY OF THE INVENTION

The following is a simplified summary providing an initial understandingof the invention. The summary does not necessarily identify key elementsnor limit the scope of the invention, but merely serves as anintroduction to the following description.

Various aspects of the present invention provide multicore fibers andendoscope configurations, along with corresponding production and usagemethods, which any of adiabatically tapered proximal fiber tips and/orproximal optical elements, for improving the interface between themulticore fiber and the sensor, photonic crystal fiber configurationswhich reduce the attenuation along the fiber, jointed rigid linksconfigurations which reduce attenuation while maintaining requiredflexibility and optical fidelity, image processing methods, spectralmultiplexing approaches, which increase the information content of theradiation delivered through the fibers and endoscope, as well asfiber-based wave-front sensors.

These, additional, and/or other aspects and/or advantages of the presentinvention are set forth in the detailed description which follows;possibly inferable from the detailed description; and/or learnable bypractice of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of embodiments of the invention and to showhow the same may be carried into effect, reference will now be made,purely by way of example, to the accompanying drawings in which likenumerals designate corresponding elements or sections throughout.

In the accompanying drawings:

FIG. 1A is a high level schematic illustration of a multicore imagingfiber having a proximal tapered end, according to some embodiments ofthe invention.

FIG. 1B is a high level schematic illustration of a multicore imagingfiber having a proximal optical element, according to some embodimentsof the invention.

FIG. 2 is a high level schematic illustration of a cross section of amulticore photonic crystal fiber, according to some embodiments of theinvention.

FIG. 3 is a high level schematic illustration of a hybrid endoscope,according to some embodiments of the invention.

FIGS. 4A-4D are high level schematic illustrations of an endoscope andillumination sources thereof, according to some embodiments of theinvention.

FIGS. 5A-5C are high level schematic illustrations of endoscopes andillumination sources thereof, configured to implement wavelengthmultiplexing super resolved imaging, according to some embodiments ofthe invention.

FIG. 6 is a high level schematic illustration of endoscopes withmultimode, multicore illumination fibers, according to some embodimentsof the invention.

FIGS. 7A and 7B are high level schematic illustrations of endoscopeswith multicore fibers with multimode cores having tens of modes,according to some embodiments of the invention.

FIGS. 8A and 8B are high level schematic illustrations of endoscopeswith enhanced field of view, according to some embodiments of theinvention.

FIGS. 9A-9C are high level schematic illustrations oflongitudinally-sensing endoscopes, according to some embodiments of theinvention.

FIG. 10 is a high level schematic illustration wave-front sensingendoscopes, according to some embodiments of the invention.

FIG. 11 is a high level flowchart illustrating a method, according tosome embodiments of the invention.

DETAILED DESCRIPTION OF THE INVENTION

In the following description, various aspects of the present inventionare described. For purposes of explanation, specific configurations anddetails are set forth in order to provide a thorough understanding ofthe present invention. However, it will also be apparent to one skilledin the art that the present invention may be practiced without thespecific details presented herein. Furthermore, well known features mayhave been omitted or simplified in order not to obscure the presentinvention. With specific reference to the drawings, it is stressed thatthe particulars shown are by way of example and for purposes ofillustrative discussion of the present invention only, and are presentedin the cause of providing what is believed to be the most useful andreadily understood description of the principles and conceptual aspectsof the invention. In this regard, no attempt is made to show structuraldetails of the invention in more detail than is necessary for afundamental understanding of the invention, the description taken withthe drawings making apparent to those skilled in the art how the severalforms of the invention may be embodied in practice.

Before at least one embodiment of the invention is explained in detail,it is to be understood that the invention is not limited in itsapplication to the details of construction and the arrangement of thecomponents set forth in the following description or illustrated in thedrawings. The invention is applicable to other embodiments that may bepracticed or carried out in various ways as well as to combinations ofthe disclosed embodiments. Also, it is to be understood that thephraseology and terminology employed herein are for the purpose ofdescription and should not be regarded as limiting.

Unless specifically stated otherwise, as apparent from the followingdiscussions, it is appreciated that throughout the specificationdiscussions utilizing terms such as “processing”, “computing”,“calculating”, “determining”, “enhancing”, “deriving” or the like, referto the action and/or processes of a computer or computing system, orsimilar electronic computing device, that manipulates and/or transformsdata represented as physical, such as electronic, quantities within thecomputing system's registers and/or memories into other data similarlyrepresented as physical quantities within the computing system'smemories, registers or other such information storage, transmission ordisplay devices. Any of the disclosed modules or units may be at leastpartially implemented by a computer processor.

Multicore fibers and endoscope configurations are provided, along withcorresponding production and usage methods. Various configurationsinclude an adiabatically tapered proximal fiber tip and/or proximaloptical elements for improving the interface between the multicore fiberand the sensor, photonic crystal fiber configurations which reduce theattenuation along the fiber, image processing methods and jointed rigidlinks configurations for the endoscope which reduce attenuation whilemaintaining required flexibility and optical fidelity. Variousconfigurations include spectral multiplexing approaches, which increasethe information content of the radiation delivered through the fibersand endoscope, and configurations which improve image quality, enhancethe field of view, provide longitudinal information. Variousconfigurations include fiber-based wave-front sensors. Many of thedisclosed configurations increase the imaging resolution and enableintegration of additional modes of operation while maintain theendoscope very thin, such as spectral imaging and three dimensionalimaging. It is noted that while the following refers to tissue as theimaging object, any other element, object, surface or part may be imagedby the disclosed fibers and endoscopes, and the term “tissue” is not tobe taken as limiting the invention in any way. It is further noted thatconfigurations are disclosed separately to merely to simplify therespective explanations, and configurations may be combined to forendoscopes with two or more of the configurations which may beillustrated in different figures and/or disclosed in differentembodiments,

Tapered End

FIG. 1A is a high level schematic illustration of a multicore imagingfiber 100 having a proximal tapered end 120, according to someembodiments of the invention. Multicore imaging fiber 100 receivesradiation 95A from imaged tissue 90 (as a non-limiting example) at adistal end 100A of fiber 100, transmits the radiation throughout thefiber's length and delivers radiation 95B to a sensor 80 at a proximalend 100B of fiber 100. Multicore imaging fiber 100 may comprise a largenumber of cores 110 within a common cladding and/or multiple claddingstructures 112, e.g., multicore imaging fiber 100 may comprise tens orhundreds of thousands cores 110. FIG. 1A illustrates schematically onlyfew cores 110 for explanatory purposes. Certain embodiments compriseendoscopes comprising multicore imaging fiber 100.

For example, multicore imaging fiber 100 may comprise at least 10,000cores 110 (possibly 50,000 cores, 100,000 cores or any intermediate orother number) with a common cladding 112 and have proximal tip 100Aconfigured to deliver image radiation 95A from tissue 90 at distal end100B of fiber 100. Image radiation 105A may be confined to cores 110A(having a diameter d1, e.g., between 0.5-2 μm, between 1-1.5 μm etc.)and cores 110A may be interspaced within fiber cross-sectional area A1(having a diameter D1, with cores 110A interspaced, L1, e.g., by severalμm, e.g., 3-5 μm) to prevent cross-talk between cores 110A. Crosssection 100A may be prevalent from distal end 100A and throughout all offiber 100, but for tapered end 120 thereof, and is illustrated to showeach core 110A surrounded by cladding material or structures 112A andwith image radiation 105A confined to core 110A. It is noted that cores110 may have a varying degree of order, and may be dispersed through thefiber cross section with a certain degree of randomness. Theinterspacing, or pitch L1 between cores 110 may be understood as averageor median interspacing.

Proximal tip with tapered end 120 may be very short, e.g., shorter thane.g., 2 cm, 1 cm, 0.5 cm etc. as indicated by the length T, and beadiabatically tapered to reduce the fiber cross-sectional area (e.g.,from fiber diameter D1 and cross-sectional area A1 to a fiber diameterD2 and cross-sectional area A2) and to reduce the core diameter (e.g.,from core diameter dl of cores 110A to a core diameter d2 of cores 110B,and correspondingly pitch L1 to reduced pitch L2) by a factor of atleast 3, allowing image radiation 105B to exit narrowed cores 110B.Proximal tip with tapered end 120 may be further configured to deliverimage radiation 105B as radiation 95B to an adjacent sensor 80, with aneffective image area to sensor area ratio (A3:A2) which is much largerthan the ratio of original fiber cross sectional area to sensor arearatio (A3:A1). For example, effective image area to sensor area ratio(A3:A2) may be at least 1:3, 1:2 or even larger, possibly approaching1:1. The larger ratio of image area to sensor area enables any of: usingsmaller sensors 80 (as sensor coverage by the image is more efficient),using large sensors 80 more efficiently (with more pixels sensing imagedata) and/or using simpler sensors 80 (without gaps between pixels, asinterspaces between cores 110A are reduced and radiation 105B may bedelivered over most or all of the tapered end's cross sectional areaA2). Radiation 105B may exit smaller cores 110B at tapered end 120 todeliver radiation 95B to sensor 80 over an area which is larger than thecumulative area of cores 110B, while avoiding crosstalk due to theshortness of proximal end 100B and due to the fact that tapered end 120is mechanically fixed and cannot bend.

For example, in certain non-limiting embodiments, an effective area ofadjacent sensor 80, which receives image radiation 95B from proximal tip120, may be at least 50% of the total area (A3) of adjacent sensor 80,possibly even at least 70%, 80% or 90% thereof In certain embodiments,proximal tip 120 may be is shorter than 0.5 cm and/or stiff. In certainembodiments, reduced fiber cross-sectional area A2 may be smaller than0.1 mm², reduced core diameter d2 may be smaller than smaller than theoptical wavelength in order to cause light to get out of the core and totravel in the cladding area (e.g., smaller than 0.5 μm-500 nm, smallerthan 0.4 μm-400 nm, or other values.), and/or reduced core pitch L2 maybe smaller than 2 μm.

Advantageously, disclosed designs improve sensor efficiency usingmulticore fibers. Applying sensing array 80 to present multicore fibershaving their proximal end similar of distal end 100A—requires theimaging camera to have enough pixels to sample cores 110A as well ascladding 112A between cores 110A. Moreover, as the camera samples thespace uniformly but cores 110A are not completely ordered, regionsbetween cores 110A require waste of camera hardware, namely the sensorshave a number of pixels which is much larger than the number of cores110A in the fiber. In disclosed embodiments however, not only iscross-sectional area 100B much smaller than cross-sectional area 100A,but the spaces between cores 110B are significantly reduced or evenavoided, to deliver radiation 95B over most or all of cross-sectionalarea 100B adjacent to sensor 80 because due to the tapering the lightpropagating in the tapered section is not confined any more to the coreregion but rather leaks out to the cladding area. It is noted that whilethe spreading of radiation 105B beyond narrowed cores 110B provides moreefficient use of sensor 80, it does not result in crosstalk betweencores 110B and does not limit the bending of fiber 100, as proximaltapered end 120 is very short (and may further be made stiff to preventbending). For example, in fiber 100 having 80,000 cores 110, sensors 80may have only one or few 100,000 pixels to detect all radiation 95B,95A, while prior art fibers (having proximal cross-section 100A) mayrequire several megapixels to detect all radiation from tissue 90.

Optical Reduction of the Effective Fill Factor

FIG. 1B is a high level schematic illustration of a multicore imagingfiber 100 having a proximal optical element 122, according to someembodiments of the invention. Multicore imaging fiber 100 receivesradiation 95A from imaged tissue 90 (as a non-limiting example) atdistal end 100A of fiber 100, transmits the radiation throughout thefiber's length and delivers radiation 95B to sensor 80 at proximal end100B of fiber 100. Multicore imaging fiber 100 may comprise a largenumber of cores 110 within a common cladding and/or multiple claddingstructures 112, e.g., multicore imaging fiber 100 may comprise tens orhundreds of thousands cores 110. Sensor 80 may be part of a detector 85connected to a processing unit 180 configured to process deliveredradiation 95B and form images therefrom.

FIG. 1B illustrates schematically only few cores 110 for explanatorypurposes. Certain embodiments comprise endoscopes comprising multicoreimaging fiber 100.

For example, multicore imaging fiber 100 may comprise at least 10,000cores 110 (possibly 50,000 cores, 100,000 cores or any intermediate orother number) with a common cladding 112 and have proximal tip 100Aconfigured to deliver image radiation 95A from tissue 90 at distal end100B of fiber 100. Image radiation 105A may be confined to cores 110A(having a diameter d1, e.g., between 0.5-2 μm, between 1-1.5 μm etc.)and cores 110A may be interspaced within fiber cross-sectional area A1(having a diameter D1, with cores 110A interspaced, L1, e.g., by severalμm, e.g., 3-5 μm) to prevent cross-talk between cores 110A. Crosssection 100A may be prevalent from distal end 100A and throughout all offiber 100 and is illustrated to show each core 110A surrounded bycladding material or structures 112A and with image radiation 105Aconfined to core 110A. It is noted that cores 110 may have a varyingdegree of order, and may be dispersed through the fiber cross sectionwith a certain degree of randomness. The interspacing, or pitch L1between cores 110 may be understood as average or median interspacing.

Proximal optical element 122 may be set between distal fiber end 100Band sensor 80 and be configured to collect image radiation from cores110 into a smaller area than the area of distal fiber end 100B, toeffectively reduce the fill factor of radiation 95B reaching sensor 80(the fill factor may be seen as the ration between the image radiationdelivering cross sectional area and the total cross sectional area offiber 100). For example, proximal optical element 122 may comprise oneor more prism(s) and/or grating(s) configured to shift closer imageradiation from individual cores so that image radiation 95B reachingsensor 80 is at a smaller effective pitch than L1. In certainembodiments, delivered radiation 95B may be shifted in a way that mixingthe spatial order of cores 110, and detector 85 and/or processing unit180 may be configured to re-arrange shifted core image radiation to forma correct image. For example, prism(s) with multiple orientations orDammann grating(s) (see also FIG. 5C for an analogous solution) may beused to implement proximal optical element 122. For example, proximaloptical element 122 may be configured to reduce, optically, a fillfactor of cores 110 in the fiber cross section by re-orienting thedelivered image radiation from cores 110 to fill a smaller area onadjacent sensor 80 with respect to the area of fiber cross section 100B,e.g., to enable using sensor 80 with an area of a third or less of fibercross section 100B (e.g., the area delimited by cores 110).

It is noted that throughout the disclosure, the term “distal” is used torefer to the ends and associated parts of fiber 100 and/or endoscope 150which are far from the endoscope's interface (with the detector or theeye of the user) and close to the imaged tissue and to its surroundings,while the term “proximal” is used to refer to the ends and associatedparts of fiber 100 and/or endoscope 150 which are close to theendoscope's interface (with the detector or the eye of the user) and farfrom the imaged tissue and to its surroundings. Concerning cores 110, itis noted that cores 110 may support a single radiation mode, or incertain embodiments, cores may be multimodal, and support more than oneradiation mode, as determined by the numerical aperture (NA) anddiameter of cores 110 and the delivered wavelength.

It is further noted that fiber 100 and/or endoscope 150 in any of thedisclosed embodiments may be used for near or far filed imaging, or anyimaging position therebetween. Near field imaging refers to theformation of an image (of imaged objects, tissues and/or theirsurroundings) at the distal end of the endoscope fiber, typically at thefiber's tip. The image is then typically transferred through the fiberto the detector, possibly through proximal optical elements. Far fieldimaging refers to the formation of a Fourier transform of imagedobjects, tissues and/or their surroundings at the distal end of theendoscope fiber (e.g., the distal end of the endoscope fiber may be atthe aperture or pupil plane of the endoscope's optical system),typically at the fiber's tip. The image of the imaged objects, tissuesand/or their surroundings may be formed at the proximal end of theendoscope fiber, typically at the fiber's proximal tip or directly onthe detector, possibly through proximal optical elements. Near and/orfar field imaging may be implemented by various embodiments of opticalsystems, e.g., direct imaging without any optical elements between theimaged object or tissue and the fiber tip or imaging through any opticalelement(s) (e.g., lenses). Optical elements may be positioned betweenthe imaged object or tissue and the distal fiber tip, with the distalfiber tip being at least approximately at the Fourier plane (for farfield imaging, also termed aperture plane and pupil plane in differentcontexts) or at the focus plane (for near field imaging, also termedimage plane in different contexts) of the optical elements. Intermediateimaging may also be applicable for fiber(s) 100 and/or endoscope(s) 150,with a processing unit being configured to determine the spatialconfiguration (e.g., relative positions of the Fourier and/or imageplanes with respect to the fiber's distal tip) and process the deliveredradiation from the tissue respectively.

Improving the Resolution

In certain embodiments, endoscope 150 may be operated to provide farfield imaging, with distal tip 100A of fiber 100 being at the Fourierplane of the imaging system (deliver Fourier transform of imaged tissueas the delivered radiation), with the output resolution at detector 85determined by the number of the pixels in the delivered radiation(rather than by the number of cores 110 as in near field imaging),because the Fourier domain is sparse and a small number of cores issufficient to transmit the spectral information (especially in casescores 110 are not periodically ordered and thus the sampling of theFourier is sparse and not uniform/periodic which is even better forproperly representing the information of the object that is to beimaged). In certain embodiments, sparse sampling of the Fourier plane,by setting distal end 100A of fiber 100 at a corresponding position withrespect to tissue 90 (far field imaging) may be used to improve theresolution of resulting images, e.g., by implementing compressed sensingalgorithms, with respect to near field imaging, by overcoming thedifficulty of imaging tissue 90 that corresponds to gaps between cores110 (see e.g., pitch L1 in FIGS. 1A and 1B).

Photonic Crystal Fibers

FIG. 2 is a high level schematic illustration of a cross section of amulticore photonic crystal fiber 100, according to some embodiments ofthe invention. Certain embodiments comprise endoscopes comprisingmulticore imaging fiber 100.

In certain embodiments, multicore fiber 100 may have a photonic crystalstructure composed of multiple air holes 101 in at least two types:core-type air holes 110 interspaced within the fiber cross-sectionalarea at a specified core-pitch P1 selected to confine image radiation105 within core-type air holes 110, and cladding air-holes 112 (betweencore-type air holes 110) which are interspaced within the fibercross-sectional area at a specified cladding-pitch P2 selected toprevent cross-talk between core-type air holes 110. The core diameters(denoted by D's for core-type air holes 110 and cladding air-holes 112)may also be configured to support image radiation confinement withincore-type air holes 110 (e.g., the diameter of core-type air holes 110may be between 0.7-1 μm, e.g., 0.9 μm).

Advantageously, using air holes 101 to provide core-type air holes 110reduces the attenuation of radiation 105 travelling through cores 110which are made e.g., of polymer material such as poly(methylmethacrylate) (PMMA), polystyrene (PS) etc. Cladding air-holes 112 aredesigned to form a periodic structure around each core-type air hole 110to confine radiation 105 therein due to the spatial periodicity of thecladding structure rather than due to differences in the refractionindex as in polymer cores. In effect, multicore fiber 100 may be seen asproviding multicore photonic crystal fibers for the first time. Forexample, in certain embodiments, multicore fiber 100 may have anattenuation coefficient which is smaller by e.g., a factor of 2 perlength of 10 cm than a comparable multicore fiber having a same numberof polymer cores.

Rigid Links and Joints Structure

FIG. 3 is a high level schematic illustration of a hybrid endoscope 150,according to some embodiments of the invention. Endoscope 150 maycomprise distal multicore fiber 100 optically coupled to a plurality ofrigid image-relay elements 130, interconnected by a respective pluralityof joints 140.

Distal multicore fiber 100, e.g., an imaging fiber, may be configured toreceive image radiation 95A from tissue 90 at distal end 100A thereofand deliver the image radiation to proximal end 100B of proximalmulticore imaging fiber 100. It is notes that rigid image-relay elements130 are made of materials which are more transparent in the respectivewavelength range than core material of fiber 100, providing overallreduction of attenuation along endoscope 150 (e.g., rigid image-relayelements 130 may be made of glass while fiber cores 110 may be made ofpolymers which are less transparent). For example, rigid image-relayelements 130 may be GRIN (graded index) rods and/or lenses made ofglass.

Rigid image-relay elements 130 interconnected by respective plurality ofjoints 140, may be configured to deliver radiation travelling throughfiber 100 as radiation 95B to a detector 85 (e.g., sensor 80 withcorresponding optical element(s)). A distal one of rigid image-relayelements 130 may be connected via a corresponding joint 140A to proximalend 100B of distal multicore imaging fiber 100.

Joints 140A, 140 may be configured to preserve the delivered imageradiation from proximal end 100B of distal multicore imaging fiber 100upon angular movements 136A of rigid image-relay elements 130 withrespect to each other, to deliver the image radiation at a proximal end100C of endoscope 150.

Optionally, endoscope 150 may further comprise a proximal multicoreimaging fiber 100-1 connected to a proximal one of rigid image-relayelements 130 via corresponding joint 140B, and configured to deliver theimage radiation from proximal rigid image-relay element 130 to detector85.

Joints 140, 140A, 140B may be designed according to the illustrateddesign principles, as mechanical-optical joints which preserve theimaging condition between adjacent rigid image-relay elements 130 (aswell as thereto and therefrom, relating to joints 140A, 140B to fibers100, 100-1, respectively) so that light is continuously coupled from onelink to the next, at different angles of rotation of rigid image-relayelements 130. It is emphasized that in endoscope 150, imaging ismaintained as well as a certain degree of flexibility between rigidelements 130, which may suffice for most of the length of endoscope 150.Multicore fibers 100 may be used only at imaging end 100A of endoscope150, and possibly at its detector end 100C. Such configurations may beused to yield long endoscopes 150, without limitations resulting fromthe length of multicore fiber 100 (e.g., attenuation, price, opticalperformance etc. which at least partly are due to light attenuationthrough polymer cores 110). Endoscope 150 may further comprise sleeves(not shown) to support the disclosed structure mechanically.

In certain embodiments, at least some, or all of rigid image-relayelements 130 may comprise glass GRIN links and joints 140 may comprisespherical ball lenses 135 positioned within mechanical joints 136 whichare connected mechanically to adjacent rigid image-relay elements 130 orfibers 100, 100-1 (for joints 140, 140A, 140B, respectively). Sphericalball lenses 135 may be positioned to preserve, proximad (in proximaldirection), the delivered image radiation in any angular relationbetween adjacent rigid links 130. For example, spherical ball lens 135may be positioned in the center of mechanical sliding ring 136 indistances fulfilling the imaging condition between an exit face 130A ofone link 130 positioned on one side of joint 140 and an entrance face130B of next adjacent link 130 positioned on the other side of joint140. Alternatively, optical elements 135 may be used in place ofspherical ball lenses 135. Optical elements 135 such as spherical balllens 135 may be configured to create coupling of light from one link 130to the next link 130 for any possible angle (or angles within aspecified range which is limited mechanically) created between links130.

Spectral Multiplexing

FIGS. 4A-4D are high level schematic illustrations of endoscope 150 andillumination sources 160 thereof, according to some embodiments of theinvention.

Certain embodiments comprise endoscopes 150 comprising an illuminationsource 160 (see FIG. 4A), configured to deliver illumination 65 (e.g.,via one or more illumination fiber(s) 60) at a specified plurality ofdistinct wavelengths, detector 85 comprising a spectrometer 162 (inaddition to sensor 80 and optionally optical elements 82) configured todecode detected radiation 95B in the specified plurality of distinctwavelengths, multicore imaging fiber 100 configured to deliver, throughcores 110 to detector 85, image radiation 95A received from tissue 90illuminated by illumination 65 from illumination source 160, andprocessing unit 180 configured to derive, from the decoded detectedimage radiation of each of cores 110, image data corresponding to thespecified plurality of distinct wavelengths. Applying illumination atthe plurality of distinct wavelengths, simultaneously or sequentiallyand analyzing received images with respect to the plurality ofwavelengths for each core 110, is referred to herein as spectral, orwavelength, multiplexing.

For example, as illustrated schematically in FIG. 4B, multiple inputfibers 162 may be configured to deliver the distinct wavelengths(denoted λ₁ . . . λ_(N)) as narrowband radiation to a multiplexer 165,e.g., a wavelength-division multiplexer (WDM), which combines theradiation into illumination 65, delivered through illumination fiber 60to tissue 90. Narrowband input fibers 162 may thus be coupled throughmultiplexer 165 to deliver multiple distinct wavelengths simultaneouslyor temporally separated. Correspondingly, as illustrated schematicallyin FIG. 4C, spectrometer 170 may receive radiation 95B from multicorefiber 100 and separate it into the distinct wavelengths 172 (denoted λ₁. . . λ_(N)), by a de-multiplexer 175, e.g., a wavelength-divisionmultiplexer/de-multiplexer (WDM) (possibly even the same as WDM 165).The resulting narrowband radiation channels 172 may be delivered tosensor(s) 80, e.g., via optics 82, and the resulting data may bedelivered to processing unit 180 which may be configured to derivemultiple data channels from each core 110. Wavelength multiplexing maythus be configured to increase the information content passed througheach core 110 significantly, possibly by factors of tens, hundreds oreven thousands, depending on the number of the distinct wavelengths andthe ability to crowd narrowband wavelength ranges within the spectrumused for imaging (e.g., in the visible range of ca. 400-700 nm,bandwidths of 3 nm provide N=100 distinct wavelengths denoted λ₁ . . .λ₁₀₀).

Disclosed wavelength multiplexing may be used to enhance resolution ofendoscope 150 and/or to incorporate additional functionalities ormodalities such as OCT (optical coherence tomography), spectroscopicalanalysis etc. in addition to imaging—to implement multi-functionalmicro-endoscope 150. For example, an OCT application may be used toextract depth information for internal tissues 90. In certainembodiments, endoscope 150 may be configured to implement Fourier domainOCT with illumination source 160 being configured to have spectralscanning capability to enable capturing and processing a plurality of 2Dimages at the range of scanned wavelengths by full field Fourier domainOCT application. In certain embodiments, illumination source 160 may beconfigured to be spectrally tunable, and images at the plurality ofwavelengths may be captured and assembled by processing unit 180 aftereach (time scanning) of the range of wavelengths, to provide a 2Dspatial image with spectral information per each pixel. In certainembodiments, various spectral ranges may be scanned, e.g., fluorescencebands for fluorescent microscopy or other specific ranges—furtherenhancing the versatility and number of functionalities of endoscope150.

Multicore imaging fiber 100 and endoscope 150 may be implemented as anyof the embodiments disclosed herein, e.g., as multicore imaging fiber100 having a proximal tapered end 120, as multicore photonic crystalfibers 100 and/or as endoscope 150 with distal multicore fiber 100optically coupled to jointedly-interconnected rigid image-relay elements130.

FIG. 4D is a high level schematic illustration of temporal spectralmultiplexing in illumination source 160, according to some embodimentsof the invention. Illumination source 160 may comprise a fiber laser 162comprising a broadband Bragg filter mirror 161 for a range of thespecified plurality (N) of distinct wavelengths (denoted λ₁-λ_(N)), acontrollable 1-to-N switch 164 connected to N narrowband Bragg filterminors 167 (denoted λ₁ . . . λ_(N)), for the corresponding distinctwavelengths, each of narrowband Bragg filter mirrors 167 designed toreflect only the corresponding distinct wavelength. 1-to-N switch 164may be controlled electrically (or mechanically, optically etc.).Illumination source 160 may further comprise a pumped gain in-fibermedium 163 connected between Bragg filter mirror 161 and controllable1-to-N switch 164 with connected N narrowband Bragg filter mirrors 167.Illumination source 160 may further comprise multiplexer 165 (e.g., WDM)configured to combine illumination radiation from N narrowband Braggfilter minors 167 and provide illumination 65, delivered throughillumination fiber 60 to tissue 90—simultaneously or in a temporallytunable manner with respect to the range or sub-ranges of the distinctwavelengths.

It is emphasized that the configuration illustrated in FIG. 4D may alsobe reversed to be used as spectrometer 170, as shown schematically inFIG. 4C with respect to FIG. 4B, for example, spectrometer 170configured to provide narrow band imaging detection. In certainembodiments, narrow band imaging detection may be used for improveddiagnosis of cancerous tissues.

Alternative or complementary implementations of spectral multiplexingmay comprise a plurality of wavelength specific beam splitters orgratings, configured to provide the multiple narrowband spectral rangesat λ₁ . . . λ_(N).

Spectral multiplexing may be used to enhance any of variouscharacteristics of fiber(s) 100 and endoscope(s) 150 such as resolution,field of view, working distance, depth of focus, 3D capability etc.—bymultiplying the amount of information delivered through each core 110 bya factor of 10, 100 or even 1000 (depending on the spectral range andspectral resolution). These enhancements may be carries out with respectto one or more fiber modules in endoscope 150 and/or replace the need touse several fiber modules in the endoscope (fiber modules referring toassociated fibers 100 which handle image delivery cooperatively).Spectral multiplexing may also be used to implement super resolvedimaging achieved by various means, utilizing the multiple inputs percore 110 which correspond to the multiple wavelengths.

Wavelength Multiplexing Super Resolved Imaging

FIGS. 5A-5C are high level schematic illustrations of endoscope 150 andillumination sources 160 thereof, configured to implement wavelengthmultiplexing super resolved imaging, according to some embodiments ofthe invention. Endoscope 150 may be configured to have broadbandillumination source 160, e.g., a white light source, and comprise aspatial encoder 166 configured to split the broadband illuminationspatially, delivering different narrowband wavelength ranges todifferent locations on tissue 90 (illustrated schematically in FIG. 5Aas pattern 66, FIG. 5B illustrates a non-limiting example for pattern66). Spatial encoder 166 may comprise e.g., dispersive optical elementssuch as one or more gratings, transmissive optical elements such as oneor more prisms and/or may possibly comprise de-multiplexer 175 asdisclosed above for separating individual wavelengths λ₁ . . . λ_(N)from the broadband illumination in combination with elements such as DLP(digital light processing elements), mirror arrays etc.—and deliveringdifferent λ₁ . . . λ_(N) to different locations on tissue 90.

For example, the wavelength range λ₁ . . . λ_(N) may be scanned at afolded linear pattern 66 exemplified in FIG. 5B to cover given region90A with different locations illuminated by different wavelengths λ₁ . .. λ_(N). The spatio-spectral resolution may be configured to coverlarger region 90A with larger locations per wavelength, or smallerregion 90A with smaller locations per wavelength; or alternatively orcomplementarily, the number of distinct wavelengths (N) and/or thewavelength range (λ₁, λ_(N)) may be configured to increase or reduce thespectrally-encoded spatial resolution.

Illumination 65 may therefore be configured to be spatially encoded bywavelength, illuminating each location on tissue 90 at a differentwavelength, possibly according to a specified pattern 66. FIG. 5Cillustrates schematically a non-limiting example for the opticalimplementation of illuminating pattern 66, namely by using a firstgrating 168 for implementing the spectral raster splitting and a secondDammann-like grating 169 configured to replicate the spectral rasterencoding to fully illuminate the full field of view of tissue 90,illuminating pattern 66 on all tissue regions 90A of tissue 90(illustrated in a highly schematic manner in FIG. 5C). Spatial encoder166 may be configured to use white light illumination 64 with grating168, 169 to deliver multiple illuminating patterns 66 to all tissueregions 90A of tissue 90, with radiation from each tissue region 90Adelivered to a different core 110. Encoded radiation 65 may be deliveredto tissue 90 through one or more optical element(s) 168A, e.g.,configured to delivered focused encoded radiation 65, to project pattern66 of tissue regions 90A (with the distance of optical element(s) 168Afrom tissue 90 being equal to the focus length, F, of optical element(s)168A).

It is emphasized that fiber 100 may be configured to have sparse cores110 (see FIGS. 1A, 1B), with some or each of cores 110 receivingradiation 105A from region 90A illuminated by full pattern 66 (orpossibly a part thereof) so that the region between any two cores 110may be multiplexed with wavelengths λ₁ . . . λ_(N) to make each spatialpixel guided in core 110 include actually many spatial points ofinformation encoded by the different wavelengths according to pattern66. The resulting is image, analyzed by spatial decoder 176, maytherefore have much more spatial pixels of information than the numberof cores 110 (e.g., maximally N times the number of cores).

Radiation 95A from tissue 90 may therefore be likewise spatio-spectrallyencoded, and multicore fiber 100 may be configured to deliver radiation95A from a region 90A (indicated schematically) of tissue 90, includingmultiple wavelengths which encode different locations in region 90A, todetector 85. Each core 110 may therefore be configured (e.g., byfocusing and de-focusing) to deliver spectrally-encoded information frommultiple locations on tissue 90, e.g., region 90A). Detector 85 maycomprise spectrometer 170 (e.g., implemented as disclosed above, usingprinciples disclosed in FIGS. 4C and/or 4D) and a spatial decoder 176configured to decode spatial reflectivity information from the spectralinformation—providing N data points for each core 110. Therefore eachcore 110 may be used to deliver data for multiple pixels on sensor 80,which correspond to the spectrally encoded region 90A of tissue 90.

Certain embodiments comprise endoscope 150 comprising illuminationsource 160 comprising spatial encoder 166, configured to deliverillumination 65 at specified plurality of spatially-encoding distinctwavelengths λ₁ . . . λ_(N), with different wavelengths illuminatingdifferent locations on a tissue according to specified spatio-spectralpattern 66; detector 85 comprising spectrometer 170 and spatial decoder176, configured to decode detected radiation 95B in specified pluralityof distinct wavelengths λ₁ . . . λ_(N) according to specifiedspatio-spectral pattern 66; multicore imaging fiber 100 comprising cores110 and configured to deliver (95B), through cores 110 to detector 85,image radiation 95A received from tissue 90 illuminated by illuminationsource 160, wherein at least some, or each core 110 is configured todeliver image radiation 95A from a tissue region illuminated byspecified spatio-spectral pattern 66; and processing unit 180 configuredto derive, from spatio-spectrally decoded detected image radiation 95Bof single cores 110, image data corresponding to specified plurality ofdistinct wavelengths λ₁ . . . λ_(N) from image radiation delivered byeach core 110. In certain embodiments, spatial encoder 166 may beimplemented by first grating 168 configured to split broadband (e.g.,white light) illumination into specified plurality of distinctwavelengths λ₁ . . . λ_(N) and second grating 169 configured toreplicate the split broadband illumination to multiple patterns 66corresponding to different regions of tissue 90.

Speckle Reduction

FIG. 6 is a high level schematic illustration of endoscope 150 with amultimode, multicore illumination fiber 102, according to someembodiments of the invention. In certain embodiments, illuminationsource 160 may be configured to deliver illumination 104 through singlemode, multicore illumination fiber 102 to generate a speckle pattern 108on tissue 90 which is more uniform and with larger speckles thandifferent types of illumination, such as by a multimode illuminationfiber with a large-area core. Single mode, multicore illumination fiber102 may be configured to have about the same area as a single coremultimode illumination fiber, to deliver a comparable amount ofillumination or energy, while delivering the illumination throughmultiple cores having almost identical axial lengths of the respectivelight channels (due to the fabrication process). As the optical pathsare practically identical, resulting speckle pattern 108 consists oflarge speckles (due to interference of light coming from the differentcores which are small in dimensions) and is more uniform than singlecore multimode illumination. Advantageously, larger speckles requiresimpler speckle averaging and reduction and are therefore advantageouswith respect to resulting image quality and required processing power.Moreover, cores of single mode, multicore illumination fiber 102 may beoptimized with respect to core size and number to maximize the size ofspeckles in the illumination channel and in pattern 108. Processing ofthe distal tip of illumination fiber 102 (e.g., may also be configuredto enhance the coherence of illumination radiation delivered throughdifferent cores.

Processing unit 180 may be configured to identify and remove fromdelivered image radiation 95B, speckle pattern 108 from illumination 104by single mode, multicore illumination fiber 102.

In certain embodiments, illumination may be implemented by one or moremultimode multicore illumination fiber 102 with cores having a smallnumber of multiple modes (e.g., 2-10 modes, or few tens, e.g., 10-30modes) to provide additional flexibility in enhancing the uniformity ofthe speckle's formation altogether.

In certain embodiments, the shape of the illumination spot may bemodulated to remove secondary speckle patterns, which depend on the spotsize, by image processing. In certain embodiments, processing unit 180may be configured to modulate, via illumination source 160, illumination104 with respect to at least one illumination spot parameter such as anyof the shape, the diameter and/or the spatial modes of the illuminationspot, e.g., according to a specified pattern. Processing unit 180 may befurther configured to use the specified pattern to analyze resultingchanges in the image of the illumination spot, as detected by detector85, and remove features of the image that fluctuate according to thespecified pattern, as being related to secondary speckle patterns ratherthan to the imaged tissue. Advantageously, the contrast of the secondaryspeckle patterns may be significantly reduced and the image qualitysignificantly improved. It is noted that removable secondary specklepatterns relate to features that may be modified by modulatingillumination 104, while some residual, primary speckle patterns mayremain, such as features relating e.g., to the size of the diffuser (notshown) through which illumination 104 is performed.

Hybrid Imaging Fiber

FIGS. 7A and 7B are high level schematic illustrations of endoscope 150with multicore fiber 100 with multimode cores having tens of modes,according to some embodiments of the invention. Multicore fiber 100 maybe configured to have a relatively small number of cores, e.g., severaltens of modes (e.g., 10, 30, 50, 80) or a few hundred modes (e.g., 100,150, 200) to implement a hybrid multicore fiber 100 in the sense thatcores 110 are not single mode cores, but also not the customarymultimode cores supporting many hundreds or thousands of modes.Complementarily, processing unit 180 may comprise a mode-decouplingmodule 184, configured to remove distortions which may be caused by modemixing at bends of hybrid multicore fiber 100. Advantageously, while theuse of multimode cores increases the information content of deliveredradiation 95B, endoscope 150 does not become as sensitive to bending offiber 100 as are prior art fibers supporting thousands or even tens ofthousands of modes, because the computational effort in removing thedistortions due to mode mixing is tolerable, and achievable by availableprocessors for such applications.

When fiber 100 is bended in operation, the different modes are mixed andthe image guided by through them is distorted, yet the distortions maybe inverted by applying e.g., deep learning neural network algorithms bymode coupling module 184. Since every core 110 has small number of modes(e.g., tens of modes, much less than regular multimode fibers) theinversion of the modes-mixing due to bending may be carried out in realtime.

In certain embodiments (see e.g., FIG. 7B as a non-limiting example),illumination source 160 may be configured to project a point (or anypattern) 67 on tissue 90 and processing unit 180 may be configured toestimate distortions by analyzing a distortion of illuminated point (orpattern) 67 in its image 97 (illustrated schematically) deliveredthrough fiber 100 (within region 90B of tissue 90 imaged by fiber 100and indicated schematically as image 95B). Mode coupling module 184 maybe configured to enhance distortion cleaning calculations using thedistortion estimation of illuminated point or pattern 67.Advantageously, the overall resolution is significantly increasedwithout adding too much overload to the processing power of processingunit 180. For instance, in an illustrative non-limiting example,assuming a 450×450 micron fiber 100 with 20,000 cores 110, with everycore 110 having 100 modes, the received image (95B) would have of 2Mpixels instead of only 20K pixels when cores 110 are single mode.Certain embodiments of hybrid fiber 100 avoid both the difficulty inproducing single mode cores in the multicore fiber and the requirementfor rigidity in multimode fibers (to prevent mixing of modes which notfeasible to correct) to combine the benefits of information increasewhen using multimode multicore fibers with reduced sensitivity tobending due to the relatively small number of modes.

Field of View Enhancing and Zooming

FIGS. 8A and 8B are high level schematic illustrations of endoscope 150with enhanced field of view, according to some embodiments of theinvention. In certain embodiments, endoscope 150 may be configured tohave a large field of view without need to bend the distal tip ofendoscope 150 and fiber 100. It is noted that the common practice ofbending the distal tip of endoscope 150 to increase the field of viewrequires a large volume near tissue 90 for handling the distal tip ofendoscope 150 (due to the limited bending radius thereof), while indisclosed embodiments a much smaller volume is required to accommodatedisclosed distal tip optical elements 190 which provide a largeenhancement of the field of view. Distal tip optical elements 190 may beconfigured to be controllably displaceable with respect to each other(perpendicularly to their optical axes), with relative displacement 192Aconfigured to change the field of view (192B) of fiber 100, asillustrated schematically in FIG. 8A.

As illustrated schematically in FIG. 8B, in a non-limiting example,distal tip optical elements 190 may comprise a first lens 191A with anegative focal length and a second lens 191B with a positive focallength at distal tip 100A of fiber 100. Shifting 192A of the relativeposition of lenses 191A, 191B may be configured to implement a tunableprism (see Equation 1 below). With distal tip optical elements 190,shifting (192A) lenses 191A, 191B with respect to each other increasesthe field of view (192B) of endoscope 150 by increasing only the size ofthe distal tip of endoscope 150 without requiring to bend the distal tipof endoscope 150, which requires large free volume available. Moreover,changing the distance (192A) between lenses 191A, 191B may be configuredto realize optical zooming (alternatively or possibly in addition tofield of view enhancement). A mechanism 194 may be configured to performshifts 192A between lenses 191A, 191B (perpendicularly to their opticalaxes). For example, mechanical implementations of mechanism 194 maycomprise controllably movable sleeves connected to lenses 191A, 191Band/or by springs similar to existing springs connected to thenavigation shield (not shown) of endoscope 150 which may transfer alongitudinal shift 192C of these elements to perpendicular shift 192A oflenses 191A, 191B.

The following Equation 1 demonstrates that changing a relative shiftbetween lenses 191A, 191B (left-hand expression in Equation 1) isequivalent to a prism (right-hand expression in Equation 1) with anangle that is proportional to the amount of the relative shift (192A)between lenses 191A, 191B, with T(x) denoting the overall transmissionexpression of lenses 191A, 191B as illustrated schematically in FIG. 8B,having the same focal length F in absolute value (lens 191A with −F and191B with +F), positioned sequentially with a relative transversal shiftof 2Δx between them, and λ denoting the optical wavelength.

$\begin{matrix}{{T(x)} = {{{\exp \left( {{- \pi}\; i\frac{\left( {x - {\Delta \; x}} \right)^{2}}{\lambda \; F}} \right)}{\exp \left( {\pi \; i\frac{\left( {x + {\Delta \; x}} \right)^{2}}{\lambda \; F}} \right)}} = {\exp \left( \frac{4\pi \; i\; \Delta \; x\mspace{14mu} x}{\lambda \; F} \right)}}} & {{Equation}\mspace{14mu} 1}\end{matrix}$

The overall transmission expression of the emulated prism (right-handexpression in Equation 1) reflects a prism positioned on the apertureplane of an imaging lens which shifts the obtained image by a factor of2Δx which is exactly the relative shift between two lenses 191A, 191B.By tuning (192A) the amount of shift (by changing Δx), the field of viewof fiber 100 may be scanned, providing a larger field of view thanmerely the physical field of view of the given imaging lens.

Longitudinally-Sensing Endoscope

FIGS. 9A-9C are high level schematic illustrations oflongitudinally-sensing endoscope 150, according to some embodiments ofthe invention. hi certain embodiments, endoscope 150 may be configuredto have sensing capabilities along at least part of its length. Forexample, fiber 100 may be configured to have a plurality of peripheralradiation entrance locations 195 (“windows”), configured to allowradiation from the sides of fiber 100 to enter peripheral cores 110C offiber 100, as illustrated schematically in FIGS. 9A-9C. Differentperipheral cores 110C may be configured along fiber 100 to receiveradiation 95C from different locations, e.g., from locations along abody conduit 91 such as a blood vessel, by corresponding configurationof peripheral radiation entrance locations 195 along endoscope 150.Illumination fiber 60 may be configured to emit radiation 65A alongendoscope 150, to improve or enable sensing reflected radiation 95C fromsurrounding tissue 91 by fiber 100.

For example, peripheral radiation entrance locations 195 may be arrangedin circles 195, each circle 195 being connected to a differentperipheral core 110C as illustrated schematically in FIG. 9B. Suchconfigurations may be used to extract the distance of fiber 100 fromtissue 91 along its longitudinal axis by extracting the readout ofperipheral cores 110C while internal cores 110 are used to imagingexplained above. The longitudinal sensing may therefore be used toimprove the control of endoscope 150, avoiding lateral damage to tissue91 and provide data concerning tissue 91. In certain embodiments,peripheral radiation entrance locations 195 such as circles 195 may beformed by controlled twisting of the pre-form during its drawing toyield fiber 100. FIG. 9C provides a non-limiting example for such actualfiber 100 with slits 195 produced by the inventors.

Endoscope 150 may further comprise processing unit 180 configured toderive longitudinal data 198 from radiation 95C delivered through thespecified peripheral cores, in addition to image data 197 delivered fromthe distal tip of fiber 100. Illumination fiber 60 may correspondinglybe configured to emit radiation 65A along endoscope 150, in addition toilluminating 65 tissue 90 at the distal end thereof. Endoscope 150 maybe further configured, e.g., via processing unit 180, to deriveindications for tissue 91 in proximity to fiber 100 along its length.

Wave-Front Sensing

FIG. 10 is a high level schematic illustration wave-front sensingendoscopes 150, according to some embodiments of the invention.

Endoscope 150 may comprise illumination source 160, configured todeliver illumination 65 at a specified plurality of spatially distinctlocations on tissue 90, detector 85 and multicore imaging fiber 100comprising multimode cores 110 which are configured to support more thanone radiation mode in core 110, e.g., any of 2-6 modes, or possiblybetween 2-10 or 2-20 modes (configured, without being bound by theory,according to V=π·A·(NA/λ)², with V the number of modes, λ the crosssectional area of core 110, NA the numerical aperture of core 110 and λthe corresponding wavelength, see the detailed analysis below).Multicore imaging fiber 100 may be configured to deliver, throughmultimode cores 110 to detector 85, wave-front radiation 96 receivedfrom tissue 90 illuminated by illumination source 180. Wave-frontradiation 96 may be delivered though cores 110 without any opticalelements at distal fiber tip 100A, or as modified wave-front radiation96A which may be modified by optical elements 114 between distal fibertip 100A and tissue 90 (e.g., perforations, lenslets, Shack Hartmanninterferometer configurations, pinholes array configurations, etc.). Forexample, optical elements 114 may be configured to focus sections ofwave-front radiation 96 into cores 110, to generate modified wave-frontradiation 96A in which phase information in wave-front radiation 96 ismodified to spatial information (e.g., orthogonal focus pointtranslations illustrated schematically by the double-headed arrow),which is delivered through cores 110 along multicore fiber 100.Endoscope 150 may further comprise processing unit 180 configured toderive, from the delivered wave-front radiation 96 and/or 96A, threedimensional (3D) image data 182 derived from wave-front radiation 96,e.g., according to spot position changes associated with each or some ofcores 110. The spot position changes indicate the angle of thewave-front entering respective cores 110.

An example for such configurations follows. The number of modessupported by multimode cores 110 may be selected as a tradeoff betweeninformation delivery capacity of cores 110 and the sensitivity of thedelivered modes to bending of fiber 100 (e.g., configurations less proneto bending, cores 110 may be configured to support more modes). Thistradeoff is described below, and fibers 100 may be configured toimplement various tradeoffs, with cores supporting a range of number ofmodes. The number of modes (V) may be expressed by Equation 2, with NAdenoting the numerical aperture, a is the radius of a core, λ denotingthe wavelength of the light, and n_(core) and n_(cladding) denoting thecorresponding refractive indices.

$\begin{matrix}{V = {{\frac{2\pi \; a}{\lambda}{NA}} = {\frac{2\pi \; a}{\lambda}\sqrt{n_{core}^{2} - n_{clading}^{2}}}}} & {{Equation}\mspace{14mu} 2}\end{matrix}$

The single mode condition requires V<2.405 and the number of modes (M)is proportional to 2·(V/2.405)², or specifically for a step index fibersM=4V²/π². The tradeoff of the number of modes with respect to crosstalkbetween cores 110 may be expressed in terms of the width of the Gaussianprofile of the field propagating through optical core 110 (denoted by W,defined for a field value that is 1/e of its maximal value) and thepitch L between cores 110—expressed in Equations 3 in terms of V (numberof modes) and a (core radius). For example, a condition for preventingcrosstalk between cores 110 may be defined as L≥2W, providing a relationbetween pitch (L) and core radius (a).

$\begin{matrix}{{W = {a\left( {0.65 + \frac{1.619}{V^{1.5}} + \frac{2.879}{V^{6}}} \right)}};{L = {2{a\left( {0.65 + \frac{1.619}{V^{1.5}} + \frac{2.879}{V^{6}}} \right)}}}} & {{Equations}\mspace{14mu} 3}\end{matrix}$

Such condition may be balanced in fiber design with respect to the 3Dresolution achievable by the core multimode configuration, which may beexpressed as follows. The 3D resolution in space equals to the pitchsize L (related to the core size) and the resolution in phase φsensitivity to wavefront 96 equals to 2π/√M in every axis (y and x).Thus, the angular sensitivity in the direction of propagation along theaxial direction Z, Δθ_(z), may be expressed and approximated andexpressed in to Equation 4.

$\begin{matrix}{{{\Delta\theta}_{z} \approx \frac{\pi\lambda}{4{a\left( {{0.65V} + \frac{1.619}{V^{0.5}} + \frac{2.879}{V^{5}}} \right)}} \approx \frac{1.21\lambda}{aV}} = {0.2\frac{\lambda^{2}}{{NAa}^{2}}}} & {{Equation}\mspace{14mu} 4}\end{matrix}$

The reciprocal relation between Δθ_(z) and V indicates that increasingthe number of modes (V) improves sensitivity (as smaller angles Δθ canbe sensed) but as shown above, increasing V also increases thesensitivity to fiber bending (increases crosstalk through modescoupling). The reduction in the bending angle (affects the bendingradius of the fiber) is proportional to the root of the number of modes,√M, which is proportional to 4a·NA/λ.

Equations 2-4 and the considerations presented above clearly describethe ways specific fiber configurations may be carried out to optimizeendoscope performance with respect to mechanical requirements andwave-front sensing (3D resolution) requirements. Various applications ofendoscope may imply different fiber configurations with respect to fiberrigidness, core parameters (size and pitch) and achieved spatialresolution.

It is noted that wave-front sensing endoscopes 150 may be implemented asany of the embodiments disclosed herein, e.g., as multicore imagingfiber 100 having a proximal tapered end 120, as multicore photoniccrystal fibers 100 and/or as endoscope 150 with distal multicore fiber100 optically coupled to jointedly-interconnected rigid image-relayelements 130.

FIG. 11 is a high level flowchart illustrating a method 200, accordingto some embodiments of the invention. The method stages may be carriedout with respect to endoscopes 150 and/or fibers 100 described above,which may optionally be configured to implement method 200. Method 200may be at least partially implemented by at least one computerprocessor. Certain embodiments comprise computer program productscomprising a computer readable storage medium having computer readableprogram embodied therewith and configured to carry out of the relevantstages of method 200. Method 200 may comprise stages for producing,preparing and/or using device endoscopes 150 and/or fibers 100, such asany of the following stages, irrespective of their order.

Method 200 may comprise adiabatically tapering a proximal tip of amulticore imaging fiber (stage 210) comprising at least 10,000 coreswith a common cladding, configured to deliver image radiation fromtissue at a distal end of the fiber, wherein the image radiation isconfined to the cores and the cores are interspaced within a fibercross-sectional area to prevent cross-talk therebetween, and configuringthe adiabatically tapered proximal tip (stage 215) to be shorter than 1cm and have a fiber cross-sectional area and a core diameter which arereduced by a factor of at least 3 with respect to the multicore imagingfiber, to allow the image radiation exit the narrowed cores and deliverthe image radiation to an adjacent sensor. Certain embodiments comprisereducing, optically, the fill factor of the delivered image byre-orienting delivered image radiation from the cores to fill a smallerarea on the sensor (stage 217).

Method 200 may comprise configuring multicore fiber from a photoniccrystal structure (stage 220) composed of multiple air holes, bydesigning the air holes to be in at least two types: core-type airholes, interspaced within a fiber cross-sectional area at a specifiedcore-pitch selected to confine image radiation within the core-type airholes, and cladding air-holes between the core-type air holes, thecladding air-holes interspaced within the fiber cross-sectional area ata specified cladding-pitch selected to prevent cross-talk between thecore-type air holes.

Method 200 may comprise configuring an endoscope from a distal multicoreimaging fiber and a plurality of rigid image-relay elements (stage 230),wherein the distal multicore imaging fiber is configured to receiveimage radiation from tissue at a proximal end thereof and deliver theimage radiation to a distal end of the distal multicore imaging fiber,and interconnecting the rigid image-relay elements by a respectiveplurality of joints (stage 235), wherein a distal one of the rigidimage-relay elements is connected via a corresponding joint to theproximal end of the distal multicore imaging fiber. The joints areconfigured to preserve the delivered image radiation from the proximalend of the distal multicore imaging fiber upon angular movements of therigid image-relay elements with respect to each other, to deliver theimage radiation at a proximal end of the endoscope. Method 200 mayfurther comprise connecting a proximal multicore imaging fiber (stage237) to a proximal one of the rigid image-relay elements via acorresponding joint, to deliver the image radiation from the proximalrigid image-relay element.

Method 200 may comprise using spectral multiplexing to enhance theinformation content of the delivered radiation (stage 240) and encoding,spectrally, the radiation delivered through each of the cores, anddecoding therefrom multiple data points per core (stage 245). Forexample, method 200 may comprise illuminating tissue by a specifiedplurality of distinct wavelengths, delivering image radiation receivedfrom illuminated tissue through each of a plurality of cores of amulticore imaging fiber, decoding, for each of the cores, detectedradiation in the specified plurality of distinct wavelengths, andderiving from the decoded detected image radiation of each of the cores,image data corresponding to the specified plurality of distinctwavelengths. Method 200 may further comprise implementing super resolvedimaging utilizing multiple inputs per core which correspond to themultiple wavelengths (stage 247).

Method 200 may comprise using spatio-spectral encoding and decoding ofillumination to enhance spatial resolution by spatio-spectral patternedillumination (stage 250), e.g., by illuminating tissue by a specifiedplurality of distinct wavelengths at a specified spatio-spectralpattern, delivering image radiation received from illuminated tissuethrough each of a plurality of cores of a multicore imaging fiber,decoding, for each of the cores, detected radiation in the specifiedplurality of distinct wavelengths according to the specifiedspatio-spectral pattern, and deriving from the decoded detected imageradiation of each of the cores, image data corresponding to thespecified plurality of distinct wavelengths and according to thespecified spatio-spectral pattern.

Method 200 may comprise illuminating the tissue by a single mode,multicore illumination fiber to increase speckle size and possiblyremoving speckle effects (stage 260), e.g., by using a single mode,multicore illumination fiber to illuminate a tissue imaged by amulticore imaging fiber and optionally identifying and removing fromimage radiation delivered by a multicore imaging fiber, a specklepattern from the illumination by the single mode, multicore illuminationfiber. Method 200 may further comprise modulating the shape of theillumination spot and removing secondary speckle patterns, which dependon the spot size, by image processing (stage 262).

Method 200 may comprise imaging an illuminated tissue by a multicoreimaging fiber having cores configured to support between 10-100 modes,and decoupling the modes by removing mode-mixing distortions from imageradiation delivered by the fiber (stage 270).

Method 200 may comprise increasing a field of view of an imaging fiber(stage 280) by implementing a tunable prism at a distal tip thereof,e.g., by controllably displacing distal tip optical elements withrespect to each other to change a field of view of the fiber, possiblyusing distal tip optical elements with opposite focal lengths +F and −F.

Method 200 may comprise introducing radiation laterally into peripheralcores to derive indications of the proximity of surrounding tissue(stage 290), e.g., by enabling radiation to enter through sides of amulticore imaging fiber and into specified peripheral cores thereof, andderiving longitudinal data concerning tissue surrounding the fiber fromradiation delivered through the specified peripheral cores. For example,method 200 may comprise designing peripheral slits in the fiber toenable the radiation enter the specified peripheral cores.

Method 200 may comprise implementing wave-front sensing by a multicoreimaging fiber having at least 10,000 multimode cores, by detecting imageradiation delivered therethrough, measuring a spot position associatedwith the cores and deriving 3D image data therefrom (stage 300).

In the above description, an embodiment is an example or implementationof the invention. The various appearances of “one embodiment”, “anembodiment”, “certain embodiments” or “some embodiments” do notnecessarily all refer to the same embodiments. Although various featuresof the invention may be described in the context of a single embodiment,the features may also be provided separately or in any suitablecombination. Conversely, although the invention may be described hereinin the context of separate embodiments for clarity, the invention mayalso be implemented in a single embodiment. Certain embodiments of theinvention may include features from different embodiments disclosedabove, and certain embodiments may incorporate elements from otherembodiments disclosed above. The disclosure of elements of the inventionin the context of a specific embodiment is not to be taken as limitingtheir use in the specific embodiment alone. Furthermore, it is to beunderstood that the invention can be carried out or practiced in variousways and that the invention can be implemented in certain embodimentsother than the ones outlined in the description above.

The invention is not limited to those diagrams or to the correspondingdescriptions. For example, flow need not move through each illustratedbox or state, or in exactly the same order as illustrated and described.Meanings of technical and scientific terms used herein are to becommonly understood as by one of ordinary skill in the art to which theinvention belongs, unless otherwise defined. While the invention hasbeen described with respect to a limited number of embodiments, theseshould not be construed as limitations on the scope of the invention,but rather as exemplifications of some of the preferred embodiments.Other possible variations, modifications, and applications are alsowithin the scope of the invention. Accordingly, the scope of theinvention should not be limited by what has thus far been described, butby the appended claims and their legal equivalents.

1. An endoscope comprising: All a multicore imaging fiber comprising at least 10,000 cores with a common cladding and configured to deliver image radiation at a distal end of the fiber, wherein the image radiation is confined to the cores and the cores are interspaced within a fiber cross-sectional area to prevent cross-talk therebetween; a sensor adjacent to a proximal tip of the multicore imaging fiber; and a re-orienting element for re-orienting the delivered image radiation from the cores to fill an area on the adjacent sensor that is smaller than a cross-section area of the multicore imaging fiber.
 2. The endoscope of claim 1, wherein an effective area of the adjacent sensor, which receives the image radiation from the proximal tip, is at least 50% of a total area of the adjacent sensor.
 3. The endoscope of claim 1, wherein the re-orienting element comprises a proximal tip of the multicore imaging fiber that is adiabatically tapered to reduce the fiber cross-sectional area and reduce the diameter of each of the cores.
 4. The endoscope claim 3, wherein the reduced fiber cross-sectional area is smaller than 0.1 mm², the reduced core diameter is smaller than 0.5 μm, and a reduced core pitch is smaller than 2 μm. 5-6. (canceled)
 7. The endoscope of claim 1, wherein the re-orienting element comprises a proximal optical element.
 8. The endoscope of claim 7, wherein the proximal optical element comprises at least one prism or at least one grating. 9-10. (canceled)
 11. A method comprising reducing, optically, a fill factor of cores in a fiber cross section of a multicore imaging fiber comprising at least 10,000 cores with a common cladding, configured to deliver image radiation at a distal end of the fiber, wherein the image radiation is confined to the cores and the cores are interspaced within a fiber cross-sectional area to prevent cross-talk therebetween, by re-orienting the delivered image radiation from the cores to fill an area on an adjacent sensor which is smaller with respect to an area of the fiber cross section.
 12. The endoscope of claim 1, wherein the multicore fiber comprises a photonic crystal structure composed of multiple air holes of at least two types: core-type air holes, interspaced within a fiber cross-sectional area at a specified core-pitch selected to confine image radiation within the core-type air holes, and cladding air-holes between the core-type air holes, the cladding air-holes interspaced within the fiber cross-sectional area at a specified cladding-pitch selected to prevent cross-talk between the core-type air holes.
 13. The endoscope of claim 12, wherein the multicore fiber comprises comprises more than 10,000 core-type air holes.
 14. The endoscope of claim 12, wherein the multicore fiber has an attenuation coefficient which is smaller by a factor of 2 for length of 10 cm than a comparable multicore fiber having a same number of polymer cores.
 15. (canceled)
 16. A method comprising configuring multicore fiber from a photonic crystal structure composed of multiple air holes of at least two types: core-type air holes, interspaced within a fiber cross-sectional area of the multicore fiber at a specified core-pitch selected to confine image radiation within the core-type air holes, and cladding air-holes between the core-type air holes, the cladding air-holes interspaced within the fiber cross-sectional area of the multicore fiber at a specified cladding-pitch selected to prevent cross-talk between the core-type air holes.
 17. An endoscope comprising: a distal multicore imaging fiber, configured to receive image radiation at a proximal end thereof and deliver the image radiation to a distal end of the distal multicore imaging fiber, and a plurality of rigid image-relay elements, interconnected by a respective plurality of joints, wherein a distal one of the rigid image-relay elements is connected via a corresponding joint to the proximal end of the distal multicore imaging fiber, wherein the joints are configured to preserve the delivered image radiation from the proximal end of the distal multicore imaging fiber upon angular movements of the rigid image-relay elements with respect to each other, to deliver the image radiation at a proximal end of the endoscope.
 18. The endoscope of claim 17, further comprising a proximal multicore imaging fiber connected to a proximal one of the rigid image-relay elements via a corresponding joint, and configured to deliver the image radiation from the proximal rigid image-relay element.
 19. The endoscope of claim 17, wherein the rigid image-relay elements are glass GRIN (gradient index) links and the joints comprise spherical ball lenses positioned within mechanical joints, wherein the mechanical joints are connected mechanically to the adjacent rigid image-relay elements or fibers, and the spherical ball lenses are positioned to preserve, proximad, the delivered image radiation.
 20. A method comprising: configuring an endoscope from a distal multicore imaging fiber and a plurality of rigid image-relay elements, wherein the distal multicore imaging fiber is configured to receive image radiation from tissue at a proximal end thereof and deliver the image radiation to a distal end of the distal multicore imaging fiber, and interconnecting the rigid image-relay elements by a respective plurality of joints, wherein a distal one of the rigid image-relay elements is connected via a corresponding joint to the proximal end of the distal multicore imaging fiber, wherein the joints are configured to preserve the delivered image radiation from the proximal end of the distal multicore imaging fiber upon angular movements of the rigid image-relay elements with respect to each other, to deliver the image radiation at a proximal end of the endoscope.
 21. The method of claim 20, further comprising connecting a proximal multicore imaging fiber to a proximal one of the rigid image-relay elements via a corresponding joint, to deliver the image radiation from the proximal rigid image-relay element. 22-52. (canceled) 